This invention relates to a bus-bar structure and, more particularly, to a bus-bar structure having a noise filtering function.
There has so far been known a current feeding method in a frame apparatus employing a bus bar, in which a layered bus bar is secured via an insulator to the apparatus and interconnects a bus-bar frame grounding layer and a casing frame grounding by a frame grounding connection cable. FIG. 4 shows a typical conventional bus bar of this type in a perspective view.
In FIG. 4, 19 denotes a bus bar, 20 a vinyl band for securing the bus bar, 21 a bus bar support (supporting portion), 22 frame grounding for an apparatus casing and 23 denotes a frame grounding connection cable. That is, the bus bar 1 is secured to the a bus bar support 21 with a bus bar securing vinyl band 20 as an insulating material, whilst a frame grounding layer of the bus bar 19 is connected by the frame grounding connection cable 23 to the frame grounding layer of the bus bar 19 and to the casing frame grounding 22.
In the layered structure of this conventional bus bar, there lacked suitable means to absorb the noise. As another bus bar structure, there is proposed in, for example, the JP Patent Kokai JP-A-3-81671(1991), a power supplying structure to a circuit board including a power source, the circuit board for receiving the power from the power source, and a bus bar arranged on the circuit board.
However, in the course of the investigations toward the present invention the following problems have been encountered. Namely, the conventional structure has the following inconveniences:
The first inconvenience is that, if a power feed line is connected to a noise-generating apparatus, the noise tends to be propagated over the power feed line to the bus bar and superimposed by the capacitative and inductive coupling of the bus bar on signals on the power feed line so as to be radiated from all power feed lines.
The reason is that the power feed route lacks in or suffers from shortage of a noise-filtering function.
The second inconvenience is that, although it might be possible to attempt to mount a noise filter independently of the bus bar configured for reducing the noise superimposed on the signals transmitted on the power feed system, it is necessary to provide a sufficient space to install therein plural large-sized noise filters and a stable grounding structure for grounding the noise filter if there are plural power feed lines of large current capacity and high voltage withstand properties.
The reason is that there lacks a space-saving type noise filter having large current capacity and high voltage withstand characteristics.
It is therefore an objective of the present invention to provide a bus bar in which the noise of the apparatus connected to the bus bar can be absorbed by the frame to reduce the noise propagated and radiated from the power feed cable and in which the structure may be reduced in size for space saving and cost reduction.
According to one aspect of the present invention, there is provided a bus bar structure having a noise filtering function, wherein a frame grounding layer of the bus bar is configured so that a frame grounding structure of the bus bar is via a low impedance connected to a frame of an apparatus, with the bus bar having a structure of absorbing the noise transmitted from the apparatus via a power feed cable.
According to a second aspect of the present invention, there is provided a bus bar structure having a noise filtering function wherein a frame grounding layer of the bus bar has a structure that is fastened to an frame of an apparatus in surface contact therewith, with the bus bar having a structure of absorbing the noise transmitted from the apparatus via a power feed cable.
In a third aspect of the present invention, there is provided a bus bar structure having a noise filtering function wherein a frame grounding layer of the bus bar is arranged adjacent to a power source layer and a power source grounding layer with a dielectric material in-between, and wherein the frame grounding layer of the bus bar is connected to a grounding frame of a casing of an apparatus.
In a fourth aspect of the present invention, there is provided a bus bar structure having a noise filtering function wherein a plurality of power feeding layers and frame grounding layers are arranged with dielectric layers in-between, the frame grounding layers are led out and bundled at least on one side or end, with the frame grounding layers being secured by fasteners to a frame of a casing of an apparatus in surface contact therewith to constitute a stable ground structure of low impedance to absorb the noise of the power feeding layers by inter-layer capacitative coupling.
Still further features of the present invention are disclosed in the dependent claims and are incorporated herein with reference threreto, on need.
According to a preferred embodiment of the present invention, there is provided a bus bar structure having a noise filtering function, wherein the bus bar structure has, in its layered structure, a plurality of frame grounding layers which are in surface contact with a casing of a frame apparatus by exchangeable set screws to constitute a stable grounding of low impedance to absorb the noise proper to a power feed layer by inter-layer capacitative coupling.
According to the present invention, in which the power feed layer and the frame grounding layer are intimately contacted with each other with a dielectric material interposed therebetween, stray inductance is significantly lowered to contribute to reduction of the broad-range noise through noise absorption in the low-impedance frame grounding structure.